krisss

I genuinely have no idea what is wrong with my laptop (not using it to post this message). It had been running reasonably slowly for a few days and whenever I left it for a few hours I would return to find that the internet browser had about 15 open windows (all really long addresses none of which led to any particular page). Internet Explorer was not working and nor was Firefox, Google Chrome was working fine. I therefore restarted the computer. Now All that I get is 'My Documents' window being opened. The rest of the screen is black. There is no toolbar, no icons, no background picture. I can open some files, not all, through either finding them from my documents (drive C, program files etc...) or by using control alt delete and 'new task'. A few days ago I had it on and returned to it to say that it was shutting down due to the presence of a trojan - Trojan.PWS.Legmir.AD/W32.Ahlem.A@mm I looked into this but it does not seem that severe to do the damage it has caused to my laptop. In addition I have tried programs like the Google Spyware remover which has noted several threats it puts in the 'high' threat category, however, whenever I click 'Fix' to the problem the laptop will shut itself down and re-set itself. It doesn't allow me to use the Google program in safe mode so I can't do it there either. Incidentally safe mode boots up in the exact same way as normal mode - with the black screen, no taskbar and no icons.
I just don't have a clue what is wrong with it and any help would be greatly appreciated.
Laptop is running vista home premium if that's any help. Any more information I'll happily provide to the best of my ability.
Thanks